Electric coupling device for thermionic valves



July 13 1926. 1,592,738 f N. LEA

ELECTRIC coUPLINGDEvIc FOR 'rHERMIoNIc vALvEs Filed Maron s; LwasInl/nier v /Varmafz ad l forrziy Patented `luly 13, 1926.

uni'ieaV stares yNORMAN LEA, OF STRAND, LONDON, ENGLAND.

ELECTRIC COUPLING DEVICE FOR THERMIONIC VALVES.

Application ined March `a, 192e, 'seriali No; sacas, and in GreatnitainJulie Y2e, 1924.

The present invention relates to the construction of a coupling devicefor .use between valves of an amplier. The'coupling device provides forwhat is commonly known nected between it and the lilanientor source ofelectrons.

The device there-fore meiitsna'mely, two resistances anda capacity. Thecombination of these three elements is in itself well known, butinorde-r to obtain the most satisfactory results ,it is important thatthey shallbe arranged in a suitable manner, and the present inventionconcerns methods of arrangement and construction.

According to this invention the two resistances are arrangedconcentrically. One resistance, which is connected to the output of theearlier valve and will be called the anode resistance, consists ofinsulated wire wound on al tubular bobbin, and the other resistance,which is connected to the control electrode of the later valve and willbe called the grid resistance, is housed inside the tubular bobbin, andthe said grid resistance may comprise a partially carbonized celluloseor like thread or may be of other convenient forni. Each resistance hasits terminals at opposite ends of the tubular bobbin, the terminals atone end being convenient for connection to the coupling` condenser andto the appropriate valve electrodes.

In order to render the performance of the device sensibly independent offrequency, it is preferable to have the anode resistance free, as far aspossible, from self-capacity and self-inducta-nce. Self-inductance canbe reduced by employing a bifilar winding well known in electricalmeasuring apparatus, but this would introduce self-capacity and alsoinsulation difficulties. Accordingly I may incorporate an anoderesistance consisting of wire wound in grooves on the tubular bobbin,the winding being alternately clockwise and anti-clockwise in theseveral grooves. In this way good insulation, small self-capacity andsmall self-inductance are obtained.

is a sectional elevation and Fig. 2 is a plan. Referring to Fig. 1. Ananode resistance bobbin l has four grooves for the windingand two eXtragrooves, one at each end, for the purpose ofmaking satisfactory endoonnections. The wire winding of the anode resistance 21'is woundclockwise and anticiockwise in alternate grooves and the ends solderedto the tag 16 and the pin 7. The l y grid resistance 2 of cartridge typewith consists of three ele-` inetal ends, is housed Within the bobbin 1and is held in position by the. clip 10 and the spring 9. The gridresistance 2 makes metallic contact with the terminal 4 via the screw 1land the clip l10 at the upper end and at the lower end is connected tothe plate 6 via the Aspring 9 and the screw 8. Ihe screw 11 is used as afixing for the terminal l. The clip 10 pivots on the screw 11 and hasits end, which engages with the conical cap of grid resistance 2, shapedas in Fig. 2, s0 that the grid resistance may be removed or inserted byturning the clip 10, but so that the clip is locked by the upward thrustimposed by the spring 9 on the grid resistance 2.

The upper end of the anode resistance is soldered to the tag 16, whichis clamped by the terminal nut 18. The terminal screw 19 has a knurledhead and is inserted from the opposite side of the bobbin l before theterminal 4t and screw 11 are in place. The two plates 5 and 6 whichconnect the anode and grid resistances respectively to the terminals 12and 13 of the condenser 17, which is housed in the case 14, are rivetedto an insulator 15. The screw 8 in addition to forming the electricalconnection for the grid resistance is also used to retain the spring 9,and to secure the bobbin` 1 t0 the insulator 15 and the plate 6. 'lli'ehole in the plate 6 which is threaded to receive the screw 8 is made byforcing metal through from one side of the sheet metal from which theplate is pressed in order to form a boss so that as long a thread aspossible is obtained. The pin 7 is used to prevent rotation of thebobbin with respect to theI insulation 15 as well as to connect theanode resistance winding to the anode plate 5.

For convenience in connecting up apparatus in which the device may'befitted the terminals 3 and 4 are placed at right angles to the terminals12 and 13, as indicated in Fig. 2. Fig. 1 is made a false section as faras the terminals 3 and 4 are concerned for ease of description.

Referring again to Fig. 1, the bobbin 1 has a cover 20 of Waterproofmaterial, on which is engraved or printed designations for the terminals3, 12 and 13, trade marks, data as to electrical values and instructionsas to how the device is to be used.

The invention is not limited to the precise arrangements described aboveand many modifications of details may be made Without exceeding thescope of the invention. For example the anode resistance bobbin 1 andthe condenser casing 14 may be moulded in one piece of a suitableinsulating material, whereby the connecting plates 5 and 6 may bedispensed with, the leads from the lower ends of the resistances beingtaken through the interior ofthe casing 14 to the terminals 12 and 13.With this construction the top or outer end of the bobbin may be closedand the tubular cavity may open into the interior of the condensercasing to permit introduction of the resistance 2.

l. A coupling device for thermionic valves comprising a condenser, acasing therefor of insulating material and forming a base member,terminals for said condenser mounted on said base member, a tubularbobbin carried by saidbase member and having a resistance Wound thereon,another resistance accommodated in said tubular bobbin, terminalsmounted on the end of the tubular bobbin remote from the base member forone end of each of said resistances, the other ends of said resistancesbeing connected one to each of the terminals for the condenser.

2. In a coupling device for thermionic valves, a condenser, a casingtherefor forming a base member, a tubular bobbin carried by said basemember and having a resistance Wound thereon, and another resistanceremovably mounted Within said bobbin.

3. In a coupling device for thermionic valves, a condenser, a casino'surrounding said condenser, a hollow bob in carried by said casing, aresistance wound on said bobbin, a second resistance mounted within saidhollow bobbin, a clip for removably retaining said second resistance inposition, and a spring for holding said second resistance in contactwith said cli In testimony Whereo I have signed my name to thisspecification.

NORMAN LEA.

